Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium. Unlike hydroponics, which uses water as a growing medium, aeroponics is conducted without a growing medium. The basic principle of aeroponic growing is to grow plants in a closed or semi-closed environment by spraying the plant's roots with a nutrient rich solution. These conditions advance plant development, health, growth, flowering, and fruiting for any given plant species. Almost any plant can grow to maturity in air in an aeroponic environment with a plentiful supply of oxygen, water, and nutrients.
Aeroponic systems provide many desirable advantages over growing systems that employ a growing medium. In general, aeroponic systems are favored over other methods because the increased aeration of the nutrient solution delivers more oxygen to plant roots, stimulating growth and helping to prevent pathogen formation.
Aeroponics can limit disease transmission since plant-to-plant contact is reduced and each spray pulse can be sterile. Where soil, aggregate, or other growing media are used, disease can spread throughout the growing media, infecting many plants. Thus, in most greenhouses and other plant growing operations such solid growing media require sterilization after each crop and, in many cases, are simply discarded and replaced with fresh, certified sterile media for each new crop. A distinct advantage of aeroponic technology is that if a particular plant does become diseased, it can be quickly removed from the aeroponic plant growing system without disrupting or infecting the other plants. Due to the disease-free environment that is unique to aeroponics, many plants can grow at higher density (plants per square meter) when compared to more traditional forms of cultivation (hydroponics, soil, etc.). Commercial aeroponic systems incorporate hardware features that accommodate crops' expanding root systems.
Aeroponic growing is considered to be safe and ecologically friendly for producing natural, healthy plants, and crops. The main ecological advantages of aeroponics are the conservation of water and energy. When compared to hydroponics, aeroponics offers lower water and energy inputs per square meter of growing area.
Aeroponic systems can be used to support the growth of plants from seed germination or from cuttings. Aeroponic culturing has revolutionized cloning (propagation from cutting) of plants. Aeroponics allows the whole process of propagation from cuttings to be carried out in a single, automated unit. Numerous plants which were previously considered difficult, or impossible, to propagate from cuttings can now be replicated simply from a single stem cutting, because the aeroponic apparatus initiates faster and cleaner root development through use of a sterile, nutrient rich, highly oxygenated, and moist environment. With the use of aeroponics, growers have cloned and transplanted air-rooted plants directly into field soil. Aeroponic roots are not susceptible to wilting and leaf loss or loss due to transplant shock (a significant problem with hydroponics). Because of their healthiness, air-rooted plants are less likely to be infected with pathogens when placed in the field.
In an aeroponic system, the plant's root zone is suspended into an environment where the roots protrude into an atomized nutrient solution, with the leaves and crown, often called the “canopy,” extending above. The roots of the plant are supported in the system by a plant support structure. Physical contact with the roots is minimized, so that the plant support structure does not hinder natural growth and root expansion or access to pure water, air exchange, and disease-free conditions. The lowest stem and root system are sprayed or misted for short durations with a hydro-atomized pure water and nutrient solution. In a true aeroponic apparatus the plant is totally suspended in air, giving the plant access to 100% of the available oxygen in the air. This maximizes the level of oxygen surrounding the stem and root system, accelerating and promoting root growth within the plant. While there is a constant available source of oxygen, the intermittent hydro-atomizing of a spray/mist of the water-nutrient solution provides the necessary moisture and essential minerals to keep plants alive and growing.
Aeroponic systems employ sprayers, misters, foggers, or other devices to create a fine mist of solution to deliver water and nutrients to plant roots. In commercial applications, a hydro-atomizing spray is employed to cover large areas of roots utilizing air pressure misting. A variation of the mist technique employs the use of ultrasonic nebulizers or foggers to mist nutrient solutions in low-pressure aeroponic devices. The key to root development in an aeroponic environment is the size of the water droplet. Water droplet size is crucial for sustaining aeroponic growth. Too large of a water droplet means less oxygen is available to the root system. Too fine of a water droplet produces excessive root hair without developing a lateral root system for sustained growth in an aeroponic system. Maintenance and the potential for component failure, such as degradation of the spray due to mineralization of mist heads, is a concern with aeroponic systems, as restricted access to water resulting from such a failure will cause aeroponically grown plants to wilt.
Various aeroponic plant growing systems have been commercially available. This includes both open systems, in which the water sprayed on the plant roots is not recycled, as well as closed systems, in which the water and nutrients sprayed on the plant roots are recovered back into a water reservoir, recycled, and reused. It is not uncommon for the spraying process in such known commercial aeroponic systems to be configured in an open loop fashion. By “open loop,” it is meant that there is only one route for water to travel from the source to the sprayer. Such commercial systems are often controlled by a microprocessor. Examples of such commercially available systems include the following.
“AEROFLO” systems (General Hydroponics, Inc., Sebastopol, Calif.) provide an aeroponic plant growing system that features an internal “laser-drilled spray line,” not individual sprayers. “AEROFLO” systems use gravity to drain the water reservoir, when needed. Each growing chamber in this system is fixedly attached to the next, limiting the ability to provide more growing space for plants as they grow larger and need more room for growth. Also, the growing chambers must be attached to the water reservoir. Because the growing chambers and reservoir cannot be separated, the water reservoir cannot be moved far from lights that are likely to be positioned above the growing chamber. This is a significant limitation for at least two reasons. Electricity is used to power the lights that are above the growing chambers. For safety purposes, electricity should be separated from the water in the reservoir as much as possible. Also, the growing lights are very hot and can heat the water in the reservoir, removing the water reservoir from beneath the lights helps to keep water temperatures down.
Aerojet systems (American Agritech, Tempe, Ariz.) provide an aeroponic plant growing system in which each growing chamber is fixedly attached to the next and in which the growing chambers are fixedly attached to the reservoir. This system features an internal manifold that requires that the entire system be shut down and torn apart to locate and fix a break in—or blockage of—the manifold. This system also relies on gravity alone to drain the water reservoir, when needed.
Aeroponic plant growing systems offered by Aero Machine (American Agritech), Apollo (Atlantis Hydroponics, Athens Ga.), Microgarden (American Agritech) and Turbogarden (American Agritech) also feature growing chambers that are fixedly attached to each other and/or fixedly attached to the water reservoir and have open sprayer line/manifold systems that are prone to fail after clogging. These systems also feature an inaccessible internal manifold and the use of gravity exclusively to drain the water reservoir.
NA Hydroponics (Granite Falls, Wash.) also offers an aeroponic system that has a built-in water reservoir and an inaccessible internal manifold.
Rainforest (General Hydroponics) offers an aeroponic system in which each growing chamber is fixedly attached to the next and which features an inaccessible internal manifold and the use of gravity alone to drain the water reservoir.
Aeroponic plant growing systems are also described in several published U.S. Patent documents, including the following.
U.S. Pat. No. 5,394,647 to Blackford, Jr. is directed to a self-contained hydroponic plant growing system. This system has a horizontal tubular chamber capped at each end and includes a series of holes along the top for supporting multiple flower pots or cups. The flower pots are suspended within the interior of the tubular chamber. The system also includes a water pump, a reservoir system, and a water delivery and spraying system. The water pump circulates water from the reservoir through spray tubes and out spray nozzles. The circulating water is absorbed by the roots of the plants hanging in the longitudinal tube. The water which is not absorbed by the plants falls onto a horizontal divider and drips through holes to the bottom of the tubular chamber. The excess water and nutrients flow through a recycle channel and back into the reservoir.
U.S. Pat. No. 5,502,923 to Bradshaw is directed to a hydroponic plant growth system which includes a circular plant module, a nutrient and water supply module, a water pump, and a water reservoir. Instead of a longitudinal tube-shaped growing chamber, the Bradshaw patent describes a circular module with the plants arranged around a center axis. Disposed along that center axis is the water and nutrient supply channel, which sprays water at the roots of the plants from a single nozzle. Non-absorbed water flows down to the lower water reservoir where it is available to be re-circulated by the water pump. An embodiment with several layers of plant modules also is described.
U.S. Pat. No. 5,724,768 to Ammann, Jr. is directed to an aeroponic plant growing system that also has a central axis, around which plants are situated. The central plant chamber includes a plurality of plant receiving apertures, which enter the central chamber perpendicularly to the central axis. Water is delivered from a sprayer located at the top of the central chamber. The water is sprayed downward and collected by the multiple perpendicularly-oriented plant holding apertures. Extra water flows down to a central reservoir at the bottom of the system.
U.S. Patent Application Publication No. 2007/0113472 to Plowman is directed to an aeroponic system for plant propagation including a plant holding chamber, a water and nutrient delivery system, and a cooling system. The chamber is a generally cube-like structure with a plurality of holes in the top layer, through which potted plants or baskets may be suspended. Within the chamber is a water delivery system with multiple spray nozzles directed toward the bottom of the pots or baskets. Within the bottom of the chamber is a water reservoir which collects the unabsorbed water. The reservoir is connected to a cooling system, which lowers the temperature of the circulating water. A water pump distributes the cooled water through the system and out of the spraying nozzles.
Although all of these systems provide for the aeroponic growing of plants with varying degrees of success, known aeroponic plant growing systems often suffer from many limitations. These include limitations in the ease or efficiency with which such known systems are operated and/or maintained, limitations in the reliability with which such systems are operated, limitations on the effectiveness with which plants may be grown in such systems, and limitations on system expandability. What is desired, therefore, is a new and improved aeroponic plant growing system that benefits from the many known advantages of growing plants in an aeroponic environment but which overcomes many of the limitations of existing aeroponic plant growing systems.